The real cost of saving time

Hi all,

I’ve just got an email from one of our clients:
The freelancer tool works really well! It has allowed me to do in 10 minutes what would have otherwise cost me half a day.

So with a simple tool we saved him half a day of work. Can you measure it in cost? Only you know how much you time is worth. But I am sure it is more than £50 ($100) that this simple tool cost him.